Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $62.33   9.130%   $68.0207   $68.02   $68.00   $68.00  
  Purchase #2 $52.38   13.212%   $59.3004   $59.30   $59.30   $59.30  
  Purchase #3 $71.44   7.516%   $76.8094   $76.81   $76.80   $76.80  
  Purchase #4 $146.97   6.752%   $156.8934   $156.89   $156.90   $156.90  
  Purchase #5 $238.26   7.308%   $255.672   $255.67   $255.65   $255.70  
  Purchase #6 $113.28   8.466%   $122.8703   $122.87   $122.85   $122.90  
  Purchase #7 $118.84   11.499%   $132.5054   $132.51   $132.50   $132.50  
  7 purchase totals = $803.50       $872.0716   $872.07   $872.00   $872.10